Raman spectroscopy and molecular reorientation in liquids: CDCl3 and CH3Br

Abstract

Raman scattering experiments on symmetrical stretching lines of liquid CDCl3 and CH3Br have been carried out at room temperature. Angular autocorrelation functions were calculated by Fourier transforming the spectra, and by eliminating the vibrational correlation function. It is found that vibrational relaxation contribution to band shapes is important for these molecules. Correlation times were found to be τ2 = 1.59 ± 0.03 psec for CDCl3 and 1.33 ± 0.07 psec for CH3Br, in agreement with previous results obtained in different ways. The times between collisions were found to be much shorter (∼ 0.01–0.03 psec) than those obtained by infrared absorption experiments but in fair agreement with recent results obtained by Bartoli and Litovitz. Second moments were found to be smaller than those predicted for pure rotational Raman bands in the classical limit. The last result may partly be explained by the important contribution of the vibrational relaxation to the band shape.